"Many of us use Google Image Search to find imagery of people, clip art for presentations, diagrams for reports, and of course symbols and patterns for artistic inspiration. Unfortunately, searching for the perfect image can be challenging if the search results match the meaning of your query but aren't in a style that's useful to you," explains Google's blog.
You can find the restrictions in the drop-down that has the default option "any content". After ignoring the content of the images and only indexing the associated text and metadata, image search engine are transitioning to a new model that involves analyzing the images, detecting objects and recognizing patterns.
